Telephone-exchange system



C. L. GOODRUM. TELEPHONE EXCHANGE SYSTEM.

APFLICAHUN HLH) SLPL14,\9 H. 1,334,447. Patented M211223,1920.

2 MEETS-SHEET I.

, E i HI- "H I l- In van/or: Char/ea L 60 odrum.

. c. L. eouuaum. TELEPHONE EXCHANGE SYSTEL'V APPLICAHUH FILED SEPT-14, I917.

1,334,447, Patefited Mar. 23, 1920.

2 SHEETS-SHEET 2.

Mvenfor; (774/700 L. Good/um by A/fj/ a busy signal to the forming him of the CHARLES L. GOODRUM, OF NEW COMPANY, INCORPORATED, YORK.

YORK, N. Y-, ASSIGNOR TO WESTERN ELECTRIC OF NEW YORK, N. Y., A CORPORATION OF NEW TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Mar. 23, 1920.

Application filed September 14, 1917. Serial No. 191,368.

To all whom it may concern Be it known that I, CHARLES L. GrooDRUM, a citizen of, the United States, residing at New Yorkg in the county of New York and State of New York, have invented'certain new and useful Improvements in Tele hone- Exchange Systems, of which the fol owing is a full, clear, concise, and exact description.

This invention ielates to telephone exchange systems employing machine switching, and is particularly adapted for use in a large system wherea connection may lead over a relatively great number of what are known as selector ortrunlclmnting switches. It frequently happens that after the callin subscriber has, by means of his finger whee partially built up a connection including a. relatively large number of these selectors, one is encountered having all the trunks in the desired group busy. Heretofore, in such event, the calling subscriber received a busy signal and had to replace his receiver, whereupon the set switches were all automatically restored to their normal positions. ()n the subscribers second attempt to set up such connection, a trunk int e group referred to may be idle, but all 0 those in the desired group of a preceding selector may be busy, so that he will be unable to build up the connection to such idle trunk.

This condition is particularlyaggravating when a connection is built up as far as a connector switch leading to a private branch exchange. If, temporarily, no-trunks to the P. B. X. are available and the callin subscriber compelled to hang up an; thereby restore all the switches, which condition is actually of frequent recurrence, then the service is condemned as poor and the operating company sufi'ers' in consequence.

The object of the present invention is the provision of means which will make it unnecessary to release a connection when all the trunks of the desired group are busy. .In the present embodiment of the invention, when a selector or trunk hunting connector finds that the entire group of trunks desired is busy, it will wait in operative relation to such group, at the same time transmitting calling party, thus inbusy condition of such connecting group, and at the instant one of the-trunks of the group becomes idle, will seize it, disthe busy tone from the calling subscribers line, whereupon the subscriber may transmit the next digit to set the selector inwhich the trunk so seized terminates or is put in instant communication with the operator of the P. B. X., if the P. B. X. is so arranged, or the subscriber may transmit the last di it to set the selective switch of the P. B. on the particular branch line desired.

The drawings consisting of two li lies, Figure 2 being placed to the right of E ig. 1, illustrate a complete connection between a calling substation and a private branch ex; change. Fig. 1 shows a calling substation and a trunk hunting selector switch embodying the vention. Fig. 2 shows a trunk hunting connector switch embodying the features of the present invention and a set of trunks leading to a private branch exchange and thence to a station within such exchange. The calling substation A is adapted upon the removal of the reoelver thereat, to be associated with a first selector indicated by and terminals 2?, t, by Whose brushes 6, b and shown. Brushes b, b

the brushes 6*, b means of a finder, terminalst, t are and terminals t, t farther on in the train, the omitted seleo tors being indicated by the dotted conductors c.

The invention will features of the present inbe more readily under indicate another selector stood by a detailed description of the operation. \Vith reference to Fig. 1, when the subscriber at substation A removes his receiver from the hook, at line finder whose brushes 6 and I) only are shown, is automatically set in, motion, seeking the terminals t, t of substation A. The calling party then operates his sender 100 to set the train of selectors preceding the tail.

When the conductors c, c substation A are extended shown, the stepping relay to the selector 101 of said solector. is energized over the following oircuit: free pole of battery, left winding of relay 101, selector side-switch arm 1 and its first'oontact, terminal 61, brush. 5, conductor 0, terminal t, brush 6, brush 71,-termione shown in deof the calling 7 15 number with 80 cape magnet 115 3-5 releasing the 50 or the secondary 60 scribe! at substation 65 waits for the busy tone to nal t, line conductor a, through the telephonic apparatus at substation A, line conductor 0, terminal t, brushes b, b, terminal 16, conductor brush If, terminal t, 5 lector side-switch arm 2 and its first mantact, right winding of relay 101, to ground. Relay 101 in attracting its armature energizes a slow relay 102. This relay at its left armature prepares a circuit for primary stepping magnet 113, and at its right armature energizes a relay 120 which interposes a break in the circuit of release magnet 107.

The subscriber now operates his sender '100, transmitting the digit of the called which the particular selector is concerned. The slow relay 102 its armatures attracted while the the line circuit. The denergized once for shown holds sender is interrupting relay 101, however, is

each interruption of the line circuit by the sender, arid at its armature and back con tact transmits impulses over the armature and front contact of relay 10-2 and the secondary elf-normal contact 103, to the primary stepping magnet 113 of the selector.

stores and maintains the action of the primary magnet 113. We

will assume in 11s case that ground is placed on the terminal 123 due to the busy condition of all trunks-in the group. This ground is extended through the armatures ltandcontacts-of relay a, a. and a, ina manxier to be hereinafterdescribed and projected thence over the brush 108, the second position contact and arm 5, the relay 117- to free ole of battery. Relay 117 opens the circuit stepping magnet to be hereinafter described, and prevents the escape magnet 115 from energizing. At'its right armature and contact relay 117 connects a source of busy tone 118 to the right winding of line relay 101, whence through the inductive action of the two windings of this relay, the busy tone is transmitted to the calling subscrihers substation.

Upon hearing this busy tone, the sub- A realizes that all of the trunks leading from the selector switch, which he has just actuatedarebusy and that the sending of further impulses at the present time would beuseless. He therefore be removed which will indicate that a trunk has become idle and that he may proceed with the connection.

Suppose a trunk whose terminals arehere marked 110, 111 and 112, becomes idle, the relay 1; will become deiinergized in. a manner to be hereinafter described and the ground upon terminal 123 will be removed, as a consequence of which relay 117 will become deenergized, the busy tone will be removed from the subscribers line and the action of the .switch will be taken up again at the point where the side switch wipers through the deenergization of the escape magnet 115 were moved into their second positions.

Since one of the trunks in the group upon which the selector has been set is now idle, side switch arm 4 in position 2 closes the following circuit: free pole of battery, secondary stepping ma at 116, its armature and back' contact, le t armature and back contact of" relay 117, right winding of magnet 115, arm 4 and its second contact to ground. The resistance of magnets 110 and 115 are so adjusted that magnet 115 energizes before magnet 116, and the magnet 116 is arranged not to open the circuit traced until near the end of its stroke, at which moment test brush 106 will have reached the test multiple 112 of the first trunk of the group. Busy trunks are those whose test terminals are grounded. Consequently as long as busy trunks are encountered, the es- -cape magnet 115 will be maintained energized over its left winding and arm 3 andqoo its second contact. VVh en an idle trunk is reached, indicated by the absence of ground on its test terminal 112, escape magnet 115 de'energizes, releasing the side switch to position 3. Arm 4 in leaving position 2, opens the stepping circuit of magnet 110, thusstopping the selector upon the terminals 110, 111 and 112 'of the seized trunk. Arms 1 and 2 of the side switch in moving into position 3, extend the calling line throu ito the selector brushes 104'and105and use -to the windings of calling supervisory relay 200, which is energized-over a circuit including the calling suhscribers substation in the well known manner, In moving off their second contactsthese arm's deinergize relay 101 which opens the circuit of relay 102. This relay however, is slow to release and before it retracts its armatures, test wire 121 is grounded at the connector switch through the energizution of'the first slow relay 201, responsive to the energizzv tion of relay 200. fhis ground is transmitted over arm 3 and its third relay 120, which maintains open 111 circuit ntact to of releasemagnet, 107 to preventpremature release of the selector. rangement is well known in the art and therefore is not shown in detail.

The ground on conductor 121 also causes This hold-over arthe seized trunk to test busy to other testand move the side switch arms into the third ing selectors and operates a relay which position. oivever, we will assume all by attracting its armature, closes one break trunks in the group leading to the desired etween the. commutator segment 123 and I. are busy, in other words, that ground as before described. relays a, a, and a", are energized. The e energization of relay 200, as menground is now projected through the armationed, causes in turn the energization of tures and contacts of relays w", a and the first slow relay 201 which prepares to the terminal 212, thence over the brush a circuit for the transmission of impulses 210, the side switch arm 213 and its secin response to the operation of the dial 100. end position contact, the right windingi' of Uponthe interruption of the busy tone, the relay 214 to free pole of battery. Relay seizure of the connector switch has taken 214 is energized and through its outer right, place, as described and the subscriber at subhand armature places a ground on the windstation A proceeds to manipulate the sender ing of escape magnet- 204 to hold it ener- 100 to send another series of impulses. At gized and thereby prevent the movement of each break in the line circuit, the relay 200 the side switch arms into their third posiretracts its armature thus transmitting an tion. impulse from ground over the armature and At this time a busy tone "is transmitted back contact of relay 200, the inner right from the source of busy tone 215' over the hand armature and front contact of relay secondary off-normal contact 216, the sec- 201, the winding of the second slow relay end position contact of side switch arm 217, 202 to free pole of battery, thereby causing the left hand winding of the called superthe second slow relay to remain energized visory relay 218 to free pole of battery, and during the sending of this series of impulses. through the inductive action of the Windin Upon attracting its iii-matures, relay 202 of this relay such busy tone is transmitted closes a circuit from ground, armature and to the calling substation A. back contact of relay 203, front contact and As before. the subscriber at this substainner right hand armature of relay 202, tion realizes that all trunks in the group Winding of escape magnet 204 to free pole which he has now selected are temporarily of battery. After the armature of relay 200 busy and he therefore waits until the busy Jo has been retracted once, the relay 202 has tone ceases. The cessation of the busy tone been energized and in turn the relay 20']: has is brought about in the following manner: also been energized. Upon each attracted one of the trunks leading to the desired P. movement of the armature of relay 200, an B. ecomes idle, and say relay 0 beimpulse will be transmitted tiom ground, comes dci iicrgized. thereby opening the 10 the armature and front contact of relay 200, circuit from ground through the winding of the left hand armature of relay 2 2, the arm relay 214 to free pole of battery. The de- 205 and its first contact winding of primary vice 219 which consists essentially of a conmagnet 206 to free pole of battery, Wherestantly rotating shaft, carrying a number or upon the shaft carrying the brushes 207 to commutator segments, causes the relay 214 10-5 210 inclusive, is rotated step by step until to be energized through its left hand windthe proper group is selected. ing until the shaft has rotated to a' certain Upon the cessation of this series of imposition. When this has occurred, the cirpulses, the second slow relay denergizes afciiit from ground tliropgh the device 219, ter a short interval and b opening the cirthe left. hand arniatu c and contact; and 0 cuit of escape ma ct 204 at its right hand left hand winding of relay 214 to free pole armature causest e deinergization of are reof battery, is opened for an instant and 1f lay 204 and the consequent movement of the the relay 214 is not energized through its side switch arms into theirsccond positions. right hand winding. it releases its arma- The subscriber at substation A now matures. The device 21.) is used for thepur- 5 'nipulates his dial to send the units pose of preventing more than one connector,

series of impulses, thereby setting the which may be set and waiting for conbrushes 207 to 210 inclusive on --the first nection to an idle trunk in the same group, trunk of the group leading to the desired from hunting at. the same tune, and is pro- P. B. X. The action of-the different revided to prevent a possible double conneclays and magnets during the sending of tion. As indicated on the drawing by the this series of impulses, is the same as that black segments of the commutators. the just described with the exception that the instants at which the circuits traced thrwgh side switch arm 205 being in connection the left llillltl wlmllllgfrf1143x214 will be. with its second contact, tlie secondary magopened, are displaced in the diflferent con- 126 net 211 is energized instead of the primary ncctor switches served by tl ie :dci'ice. magnet 206. At the end of, this series of *hen relay g1 releases its ill'nltl tlllts. a impulses, the relay 202 is again dei ncrgized circuit 15 established from ground, first test and under ordinary conditions the escape terminal in the selected group providing magnet 20% would in turn be (lo energized the first trunk is busy, to -the brush 209, 130

the side switch arm 221 and'its second position contact, back contact and inner right hand armature of relay 214 andback contact and outer armature of relay winding of relay to free pole of battery. liclay 222 attracts its armatures and establishes a circuit from ground, the front Contact and 4 right hand annaturc of relay 222, the armature and contact of secondary stepping mag- -be energized net 211, the winding of this magnet to tree pole of battery. Through the automatic operation of secondary stepping magnet 211, the brushes 2-07 to 210 are moved step by step over the terminals of the desired group until an idle trunk is encountered. Assume that the trunkconnected to terminals 220, 223, and 224 is idle. Upon the encomiter of brush 209 with terminal 220,10? should terminal 220be the first in same will 1 old true, the circuit traced through the arm 221 for the energization of relay 2 22 will be opened. Relay 222 will be deinergized in the one case or will not at all in the other case. if relay 222 were energized, during its energization a circuit is closed from ground, its front contact and left hand armature, the winding of escape magnet 204 to free pole of battery, and at its deenergization this circuit is opened. If relay is not energized at all, due to the fact that the brushes of the connector switch rest upon the terminals of the trunk which has become idle, then this circuit for the energization of escape magnet 204 is-not closed, and upon the denergization of relay 214, as before described and the consequent opening of the circuit from ground at the front contact and outermost right hand armature of relay 214, the escape inlagnet 2.04 is dei nergized; Upon retracting its armaturcs therefore, the escape magnet under any one 0' these conditions will move the side switch arms into third position, whereupon a tin ging circuit is established.

Ground is connected through the armature and back contact of ringing relay 203, the third position contact of side switch arm 29.5, the winding of escape magnct "Bil-l to free pole of battery. Ringingcurrent is gent-rated by the generator 226 and trans mitted over the circuit including the winding of marginal ringing cut-off relay 20?, front contact and right hand armature o escape magnct .204, third position contact and side switch arm hrush 208. terminal 223, thence over the selected trunk to the apparatus at the l. B. X. back to the terminal 224, the brush 207, the side switch arm 228 and its third position contact to ground. \Vhen in response to the apparatus controlled by the ringing current, the subscriber at the P. B. X. seizes this trunk in any well known manner, the current through the n) a}? gin-Lil ringing cut-off relay 203 which l'lEI'EiO- the group, the

fore was insufficient to energize this relay, is now increased to the point where said relay does become energized and upon attracting its armature, it opens the circuit of the escape magnet 20 Upon its denergization, the escape magnet moves the side switch arms into their fourth positions and connects through the arms 22'? and 228 the calling substation A to the operator at the P. B. 3. who in response to the calling subscrihers request, will in the well known manner connect him to the called substation B.

Upon 'the cessation of a conversation, the subscriber at substation A replaces his receiveron the hook as a consequence of which relay 200 is de'e ncrgized and the first slow re lay 201 is allowed to retract its armature's,

whereupon a circuit is, established frommal contact 229, the winding of release relay 230 to freepole of battery. time groun at the outer, right hand armature of relay 201 is removed from the test conductor 121, whereupon the relay 120 becomes dei nergized and sets up a circuit for the encrgizatipn of release magnet 107. The release of these selector switches upon the encrgization of their release magnets, is well known in the sit and will therefopa not he described in the present instance.

Vlltlh is claimed is:

1. in a telephone exchange system, the combination with telephone lines, an automatic selective switch havin trunk terminals arranged in groups, a sen or adapted to set said switch in operag've relation to one of said groups and means for thereupon automatically causing said switch to test the trunks of said group, of means rendered operative if all trunks of the selected group are. busy for preventing sa i testing operation from taking place, and means actuated when E1 trunk of the group becomes idle for causing said switch to test said trunks.

2. In a telephone exchange system, the

combinationwith telephone lines, afli automatic selective switch having trunk terminals arranged in groups, a sender adapted to set said switch in operative relation to one of said groups by a movement in a prinals arranged in groups, a sender adopted the Al; the Same to set said switch in operative relation to one'of said groups, means for thereupon automatically driving said switch over said group, of a relay for each trunk operated when such trunk is seized, a circuit closed when all the relays of a group are operated and including means for disabling said driving means, and means actuated when a trunk of the group becomes idle for opening said circuit to render .said driving means opera- 4. In a telephone exchange system the combination with telephone lines, an automatic selector having trunk terminals arranged in groups, primary and secondary driving means for said selector, a sender adapted to control said primary driving means to set said selector in operative relation to one of said groups, means for rendering said secondary driving means automatically operative immediately upon the termination of said primary movement, of a relay (0) for each trunk operated when the same is seized, a circuit closed upon the termination of (a) of a group are operated and including a relay (117) which operates to prevent the closure of such secondary driving means, and means actuated when one of said relays (a) becomes deenergized when the corresponding trunk be comes idle for dee'nergizing said relay (117) to render said secondary driving means opcrative.

5. In a telephone exchange system, the combination with telephone lines, an automatic selector having trunk terminals arranged in groups, primary and secondary riving circuits for said selector, an auxiliary switch associated with said selector and having commutator segments, one for each trunk group, a sender adapted to control'said primary driving circuit to place said selector in operative relation to one of said groups, means for auton'iatically rendering said secondary driving circuit operas tive upon the termination of the primary movement, a relay (a) for each trunk operated when such trunk is seized, means adapted when all the relays of a group are operated to ground the commutator seg ment of such group, a relay (117) and a circuit adapted to operate the same upon the termination of the i of said selector if the correspondin seg ment is grounded, said relay being adapted to open said secondary driving circuit and when any trunk of the group becomes idle to become dee'nergized and to close said secondary driving circuit.

6. In a telephone exchange system, the combination with automatic selective switches, means for preventing the automatic testing operation of one of said switches when all the trunks of a selected group are busy, a source of signaling current, means for notifying the calling subscriber of such busy condition automatically actuated by the busy condition of the group for connecting said source to the calling line, and means automatically actuated when one of the trunks becomes idle for rausing the switch to seize the same and disconnect said source from the calling line.

In witness whereof, I hereunto subscribe my name this 8th day of September, A. D.

CHARLES L. GOODRUM.

prunary movement 

